Automated One-Step Radiosynthesis Of The Cb1 Receptor Imaging Agent [F-18]Mk-9470

The fluorine-18-labeled positron emission tomography (PET) radiotracer [F-18]MK-9470 is a selective, high affinity inverse agonist that has been used to image the cannabinoid receptor type 1 in human brain in healthy and disease states. This report describes a simplified, one-step [F-18]radiofluorination approach using a GE TRACERlab FXFN module for the routine production of this tracer. The one-step synthesis, by [F-18]fluoride displacement of a primary tosylate precursor, gives a six-fold increase in yield over the previous two-step method employing O-alkylation of a phenol precursor with 1,2-[F-18]fluorobromoethane. The average radiochemical yield of [F-18]MK-9470 using the one-step method was 30.3 +/- 11.7% (n=12), with specific activity in excess of 6Ci/mu mol and radiochemical purity of 97.2 +/- 1.5% (n=12), in less than 60min. This simplified, high yielding, automated process was validated for routine GMP production of [F-18]MK-9470 for clinical studies.